Star shield to help find exoplanets

Thursday, 6 July 2006Reuters

The star shield approaches the line of sight to the parent star. At this stage, the bright starlight swamps the planet light in the telescope. But if the shield blocks most of the starlight, planets may be easier to find (Image: Amy Lo/Northrop-Grumman Space Technologies, Redondo Beach California)

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A huge daisy-shaped shield that would block out light from parent stars could be used to find Earth-like planets in other solar systems, a US astronomer says.

He and his team have designed a plastic 'starshade' measuring 45 metres in diameter that would orbit with a trailing telescope.

The shield would block out light from parent stars, which would normally swamp light reflected from their planets, to enable scientists to map planetary systems.

Finding other planets is very difficult because their parent stars are about 10 times brighter.

"We think this is a compelling concept, particularly because it can be built today with existing technology," says Professor Webster Cash of the University of Colorado, who outlines his proposal today in the journal Nature.

"We will be able to study Earth-like planets tens of trillions of miles away and chemically analyse their atmospheres for signs of life," he adds.

The shield, which is known as the New Worlds Observer, would be launched into an orbit about 1 trillion miles from Earth and then opened.

Three thrusters would be used to keep it steady while the telescope trailing thousands of kilometres behind follows light from distant planets as it hits the space shield.

"The New Worlds Observer is actively being studied in academia, industry and government," Cash says.

He adds that if Earth-like planets exist, the starshade could find them within the next decade.

One day, a ring of telescopes might be placed on the Moon with a fleet of orbiting starshades, Cash says. This would allow scientists to photograph distant planets.